Can the binocular vision prognosis in infantile esotropia be improved beyond the monofixation or worse outcome typically achieved with current detection and treatment methods? Can manifestation of the deviation be prevented to begin with? The present (revised) proposal will investigate the hypothesis that there are "precursor" sensory and/or oculomotor states prior to the onset of infantile esotropia which may provide the basis for affirmative answers to these questions.l The proposed study will be longitudinal in design, comprised of initial binocular vision, motor and refractive measurements in at least 825 4 to 24 week old infants at normal or high risk for esotropia, and then follow-up one and two years later to determine if esotropia has developed. Our hypothesis is that there will be a difference in one or a combination of the early measures between the population of infants who develop esotropia and those who do not. Binocular vision tests include measurement of peripheral fusion by dynamic random dot "fusiogram" or "aniseikoniagram," and stereoacuity by dynamic random dot stereogram. Eye movements will be the response measure, and eye tracking records will also be analyzed for oculomotor anomalies that may themselves constitute esotropia precursors. All study participants will receive a full clinical examination, including cycloplegic retinoscopy.